I used to play golf regularly, now hardly play, though would like to pick it up again in the future.
I think the only way to make the green fees cost effective is to have a club membership and play regularly. If you play at the weekend on a pay as you go basis, so when it's busy and therefore the discount offers aren't normally available, then yes you are going to pay around $40 around (£30 in the UK) or more, so it's the $80 to $100 a month for two rounds. If you take up a membership, I don't know US prices but UK prices are typically £1200 to £1500 a year for a standard course, then it's the equivalent of $150 a month and you can play once or twice each weekend for an effective cost of under $20 a round (plus in the week when on holiday / as other commitments allow). Your total cost is 2x higher but at least you are getting 4x as much golf for it and can play during the week as well. In the UK at least, one way to get to play free rounds on other local courses is to participate in club matches representing your club: you only pay the cost of a meal afterwards. If I were playing full time at my course I could easily play in 20 matches a year (half at home course; and not because I'm a great player, just because there are matches at different levels and the matches aren't that popular as most club golfers don't like playing to competition conditions).
So I think there's not much you can do with your current situation of playing twice a month at the weekend to cut that cost, unless you want a membership to pay 2x more and play 4x more, or you can find a way to play during the week and take advantage of discounted green fees.